1. Field of the Invention
This invention relates generally to a magnetic transducer head and more particularly relates to a magnetic transducer head utilizing magnetoresistance effect.
2. Description of the Prior Art
A conventional magnetic transducer head utilizing magnetoresistance (hereinafter, simply called MR) effect is constructed in general as, for example, shown in FIGS. 1 and 2. That is, a non-magnetic insulating substrate 1 made of, for example, sapphire is formed thereon with a MR element 2 made of a magnetic thin film having a MR effect such as Ni-Fe system alloy, Ni - Co system alloy and so forth, on which a protecting layer 3 made of, for example, SiO.sub.2 is formed. A non-magnetic insulating substrate 4 likewise made of, for example, sapphire is bonded on the protective layer 3 through adhesive agent 5 so as to interpose the MR element 2 between the substrates 1 and 4. The thin film MR element 2 is formed for its one end surface to face a contacting surface 6 with a magnetic recording medium (not shown). The thickness thereof is selected to be about several hundreds .ANG., and the length l thereof corresponding to the track width of the magnetic recording medium is selected in a range from several tens to several hundreds .mu.m. The direction to which the magnetic recording medium is moved relatively to this MR effect type magnetic transducer head is substantially coincident to the film thickness direction of the end surface of the thin film MR element 2 facing to the contacting surface 6 with the magnetic recording medium.
The playback magnetic head of such MR effect type can normally provide higher sensitivity in the reproduction of a narrow track, a short wavelength and at an ultra-slow speed playback than an ordinary playback magnetic head of electromagnetic induction type.
However, such MR effect type magnetic transducer head previously proposed may sometimes be eroded if the thin film MR element 2 comes into contact with a human body. For instance, the thin film MR element of, for example, 5 .mu.m wide is cut off even though the human body comes into contact therewith for about 1 to 10 seconds. The reason why the thin film MR element is eroded is that sweat streamed from the human body acts as electrolyte for the thin film MR element and an electrostatically induced voltage generated in the human body is applied thereto to cause current flowing through the sweat to the MR element to electrolyze the latter. The erosion of the MR element as described above occurs when the following three conditions (i) to (iii) are satisfied at the same time.
(i) The MR effect type magnetic transducer head is grounded through a low impedance (for example, the impedance is about less than 10 K.OMEGA.).
(ii) The human body comes into contact with the MR effect type magnetic transducer head under the state that the human body is electrically floated.
(iii)The human body has electrostatically induced voltage by a power source line.
In other words, when the human body is floated electrically, generally the human body is electrostatically induced by the power source line to have an induction potential (about .+-.20 V). Whereas, when the MR effect type magnetic transducer head is grounded through a low impedance, a potential difference is produced between the human body and the MR effect type magnetic transducer head. If under such state as described above the human body comes into contact with the MR effect element, current flows therethrough and hence it is electrolyzed and then cut off.
In order to prevent the MR effect element from being eroded by the contact of the human body as stated above, it may be considered that the occurrence of the electrolysis will be avoided if a part of the human body is grounded to allow the MR effect element and the human body to become equal in potential. But, even though the human body is grounded as seen in the above, there occurs such a case where the MR effect element is likely to be eroded.